diff --git a/src/Extension/Prelude.hs b/src/Extension/Prelude.hs
--- a/src/Extension/Prelude.hs
+++ b/src/Extension/Prelude.hs
@@ -260,3 +260,11 @@
     ms' <- errorFree ms
     if null ms' then mzero else return ms'
 
+-- Error reporting
+------------------
+
+-- | Mark a part of the code as unreachable.
+unreachable :: String -> a
+unreachable location =
+    error $ "reached the 'unreachable' code in " ++ location
+
diff --git a/tamarin-prover-utils.cabal b/tamarin-prover-utils.cabal
--- a/tamarin-prover-utils.cabal
+++ b/tamarin-prover-utils.cabal
@@ -2,7 +2,7 @@
 
 cabal-version:      >= 1.8
 build-type:         Simple
-version:            0.4.1.0
+version:            0.6.0.0
 license:            GPL
 license-file:       LICENSE
 category:           Theorem Provers
@@ -15,9 +15,13 @@
 
 description:        This is an internal library of the Tamarin prover for
                     security protocol verification
-                    (<hackage.haskell.org/package/tamarin-prover>). 
+                    (<hackage.haskell.org/package/tamarin-prover>).
 
 homepage:           http://www.infsec.ethz.ch/research/software#TAMARIN
+
+source-repository head
+  type:     git
+  location: https://github.com/tamarin-prover/tamarin-prover.git
 
 
 ----------------------